Java Introduction

 

Java Introduction:

Java is an open-source programming language designed for building applications across various platforms.

Purpose of Communication:

• Human Communication: English language
• Machine Communication: Programming language

-    to establish communication b/w  2 things

-   English  -->  English lang

-   Machine   --->  Programming language

Program: A collection of statements used to perform specific tasks.

• Example:
• Addition: 10+20=30
• Subtraction: 20−10=10

Java: An Object-Oriented Programming Language

This means that in Java, everything is represented in the form of objects and classes.

OOP Features:

• Object & Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

Examples of Object-Oriented Programming Languages:

• Java
• C#.NET
• Python

If any programming language supports the above OOP features, it is considered an object-oriented programming language.

Platform Independence:

Java is a platform-independent language.

Platform: Any operating system (e.g., Windows, Linux, macOS)

 

 A.java (Java Source Code)

• Run on Windows: Produces A Results (Same results)
• Run on Linux: Produces A Results (Same results)
• Run on macOS: Produces A Results (Same results)

When you compile and run a Java program, you get the same results regardless of the operating system:

Platform Dependent Languages:

For example, C language is platform dependent:

• A.c (C Source Code)
• Run on Windows: Produces A Results
• Run on Linux: Produces B Results

Note: VBScript is specific to the Windows operating system.

Java Applications:

1. Desktop Applications
• Examples: vlc.exe, Notepad (text file)
2. Web-Based Applications
• Examples: amazon.com, facebook.com
3. Mobile Applications (Android apps)
• Examples: WhatsApp, Amazon
4. ERP Applications
• Example: Salesforce
5. Automation Testing Tools
• Java can be used in various automation testing tools.

FAQ: JDK, JRE, JVM

JDK: Java Development Kit

• Used to develop and write Java programs as well as run them.
• JDK is software.

JRE: Java Runtime Environment

• Used to run Java programs only.
• Note: You cannot write or develop Java programs using JRE.
• Can be installed individually.
• When you install JDK, it includes JRE by default.
• JDK contains JRE. JRE is part of JDK.

JDK = JRE + JVM + LIB + BIN + etc.

FAQ: What is the difference between JDK and JRE?

JVM :  Java Virtual Machine

A set of programs or specifications used to execute Java programs.

 

Java was developed by James Gosling and his team at Sun Microsystems.

Sun Microsystems was later acquired by Oracle Corporation in 2010.

JDK 11 Installation Guide:

1. Download JDK 11:
• Visit the JDK 11 download page: JDK 11 Archive Downloads.
• Click on the download link for your operating system (Windows x64 in this case).

https://www.oracle.com/in/java/technologies/javase/jdk11-archive-downloads.html

 

Note :   after clicking download link >  Select checkbox 'I reviewed and accept the Oracle Technology Network License Agreement for Oracle Java SE

' --> Click on the Download button.>  Create Oracle account with y gmail  and password >  login with ur gmail >  Navigate to your Downloads folder and locate jdk-11.0.15.1_windows-x64_bin.exe.> Click download > it will download - "jdk-11.0.15.1_windows-x64_bin.exe"

Click jdk.exe file  from downloads folder> Click Next > Next  >  Finish

 

Checking if Java is Installed:

After installation, you can check if Java is properly installed on your system:

               C:\Program Files\Java\jdk-11.0.15.1

 

1. Open Command Prompt (CMD):

   Pressing 'Windows' btn +  R --> It opens 'Run' window >  Type 'cmd' > clikc 'Ok' or Press enter button >  opens 'Cmd prompt window'  in black screen

 

java -version

ex:

C:\Users\Lenovo>java -version

 

java version "11.0.15.1" 2022-04-22 LTS

Java(TM) SE Runtime Environment 18.9 (build 11.0.15.1+2-LTS-10)

Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.15.1+2-LTS-10, mixed mode)

 

Download Eclipse:

1. Visit the Eclipse Download Page.
2. Choose the appropriate version for your operating system and download Eclipse IDE.

 

Open Eclipse:

1. Extract the downloaded Eclipse package.
2. Launch Eclipse by double-clicking on the eclipse.exe (or eclipse on Linux) file.

Create Workspace:

1. When Eclipse opens, it will prompt you to select a workspace directory.
2. Choose or create a new directory where you want to store your Eclipse projects.
3. Click Launch to open Eclipse with the selected workspace.

 

 

 

Create Project:

1. Steps:

File >NEw > Other >  Search for JAva Project > Select 'Java Project > Click "Next"  >  ' Give some "Project name"  i.e "Nov182023JavaProject"  >  finish or Next>  Click Finish button >  click 'Dont create '  button > it creates new Project i.e 'Nov182023JavaProject" in 'package explorer' window in left side 

If we expand Java project,  there are 2 folders available .

  1. src

  2.JRE System Libraries

Check Project Current Location in our system:

1. Steps:
• Right-click on the project (Nov182023JavaProject) in the Package Explorer.
• Select Properties (or press Alt + Enter).
• In the Properties dialog, navigate to the Resource section.
• Under Location, you can see the current directory path where the project is stored, e.g., C:\brahma\Practise\SelniumPractiseNew\Nov2023WorkSpace\Nov182023JavaProject.
• Click the right arrow button to open the folder in your system's file explorer.

 

HW Create 2 Java Projects in Eclipse  and find the location of the project in ur system ?

 

Keywords in Java:

To learn any language, we start with the alphabets: A, B, C.

·  From alphabets, we make words: Apple, Bat, etc.

·  From words, we make sentences:

 "I like an apple." (We must follow grammar rules for valid sentences,

e.g., "Apple like I" is invalid

 

     make stmt  -  >  I like an apple  - -->  have to follow some grammar rules --> Syntax rules

                      Apple like I ---invalid stmt

                                    I apple like

 

 

A computer system does not understand human language (e.g., English)

Java language statements are translated into machine-level language (binary code: 001010101) that the system or processor understands.

System will not understand our English language -->    java lang  stmts--->    Machine Level Lang (001010101) -- (Sys or Processor understands)

 

Keywords:

Definition:

• Keywords are predefined words in the Java language.
• They are reserved words with special meanings in Java, used for specific purposes.

Examples of Keywords:

·  int: Used to store integer numbers, e.g., 10, 20, -15.

·  float: Used to store decimal numbers with an 'f' suffix, e.g., 10.23f, 4.5f.

·  double: Used to store decimal numbers, e.g., 10.23, 4.5.

·  char: Used to store a single character, e.g., 'A', 'B'.

·  boolean: Used to store boolean values, true or false.

if  -->  k/w in java , can be used write  if (condi)  stmt

else -->

for

while

break

class  --> is k/w in java lang-can be used  to define/ write  class 

 

  Syntax:

class someClassName

{

 

 

}

 

ex2:  creating some 'employee'  class

class employee

{

 

 

}

 

ex3:   create student class

class student

{

 

 

}

 

Note:

·       Without writing/defining any class, we cannot write any Java program.

• If we want to write any Java program, we must write/define a class.

 

Interface:

An interface is a keyword in Java used to define a contract that other classes can implement.

syntax :

 

interface I1

{

 

 

}

 

public

static

void

 

...etc

Create Package and Class:

A package is a collection of classes and interfaces.

• class1 + Interface1
• class2 + Interface2
• class3 + Interface3

Create Package:

Steps:

1. Select the src folder.
2. Right-click on the src folder.
3. Select New > Package.
4. Enter the name: package1.
5. Click the Finish button.

This will create a new package named package1 in the src folder.

 

Create Class:

Steps:

1. Select the package package1.
2. Right-click on package1.
3. Select New > Class.
4. Enter a class name: class1.
5. Click the Finish button.

This will create a new class named class1 in the selected package package1.

 

Create Interface :

HW :  write Navigation steps  how to create interface (same as  above)

 

HW Create 2 packages, 2 classes , 2 interfaces

         Package:  MyJavaPrograms   --->   create some classes (A, B) + interfaces (I3,I4)

         Package : MySeleniumPrograms  --> Create   some classes(C1,C2) +  interfaces (I5,I6)